I have been given ap project by my teachers to show the ratio between

i have been given ap project by my teachers to show the ratio between velocity and torque .
i.e i have to show the gear ratio in my project.
can some one tell me whether the ratio b/w torque and velocity remains constant if we use different number of gears .
also if some one can give me any advise regarding my project
shall be very thankful

Do you have a bicycle, or access to one with gears?
Gears on a bike can be used very conveniently to show how velocity, torque (AND POWER, which is very important in this respect) are related. Google "bicycle gear experiments". I did and found pages and pages of stuff.